About a dozen big-name financial firms yesterday were named as co-conspirators in an alleged scheme to rig the bids in the more-than-$2 trillion municipal-bond market, among them JPMorgan Chase, UBS and the fallen Lehman Brothers.

The banks’ names surfaced in a legal filing with the federal prosecutors in Manhattan in connection with a nearly-four-year-old Justice Department investigation of the muni-bond market.

At issue is whether the big Wall Street firms colluded to create the illusion that they were offering competitive rates on certain investment contracts that cities, states and other municipalities were buying with the cash from their bond offerings. The funds were invested in so-called guaranteed investment contracts, or GICs, and earned interest until they were needed to fund specific projects, such as building bridges or other projects.

Previously, the identities of the firms associated with the probe had not been disclosed, but were identified late Thursday when some court documents in connection with the probe were released.

The news comes six months after the federal prosecutors indicted municipal brokerage advisory firm CDR Financial Products employees David Ruben, Levi Wolmark and Evan Zarefsky for their alleged roles in the scheme.

CDR’s indictment charges the firm got undisclosed kickbacks concealed as fees from some of the banks. They ranged from $4,500 to $475,000 on at least 10 occasions between November 2001 and August 2005, according to court documents.

The Justice Department’s antitrust division is working with the FBI and the IRS’s criminal investigation division. The Securities and Exchange Commission, the Office of the Comptroller of the Currency and the Federal Reserve Bank of New York are also involved.

Other firms wrapped up in the probe include Bank of America, the former Bear Stearns, which has since been acquired by JPMorgan, General Electric and Citigroup’s Salomon Smith Barney unit.